1. Field of the Invention
The invention relates to dual polarized cross notch arrays and in particular the invention is concerned with antenna elements and a positioner and electrical contacts for locating and grounding metallized portions of unrestrained element ends with respect to the restrained element ends.
2. Description of the Prior Art
Dual polarized cross notch arrays are known. FIG. 1 shows one such array 10 which is fabricated by forming a plurality of sets of orthogonal antenna elements 12 and 16 respectively disposed on substrates 14 and 18. The first set of elements 12, such as shown in FIG. 2, is etched from a metallized layer 13 on each one of a first set of substrates 14. A similar set of elements 16, shown in FIG. 3, is formed from an etched metallized layer 15 on each one of a second set of substrates 18. Respective front and rear slots 17 and 19 extending from corresponding front and rear marginal edges 21 and 22 are formed in substrates 14 and 18 intermediate to the elements 12 and 16 in evenly spaced parallel rows. The front marginal edges 21 are unrestrained as hereinafter described. When the respective front and rear slots 17 and 19 are mated, the set of substrates 14 and 18 are arranged into orthogonal array 10 of elements having intersections 27 resulting in a so called egg crate configuration (FIG. 4). The substrates 14 and 18 of the array 10 intersect resulting in four inside corners 32 and open spaces 23. The radiator elements 12 and 16 are between the intersections and face outwardly from a planar front end 24 of the structure. The front slots 17 in the first set of substrates 14 result in separate unrestrained free ends 25 of the elements 12 at the front marginal edge 21 of the substrate 14. The elements 16 in the rear slotted substrate 18 have restrained free ends 26 at the front edge 20. The free ends 25 of the unrestrained elements 12 can thus become misaligned when the substrates 14 and 18 are assembled which can adversely upset the symmetry of the array 10. Also, continuity of the metallized layer 13 forming the ground plane between the elements 12 is broken by the front slots 17 which can cause radiation of unwanted modes.
FIG. 4 shows an ideal rectangularly aligned and symmetrical array 28 of restrained and unrestrained elements 12 and 16 looking in from the radiating side. The row spacing S.sub.r and column spacing S.sub.c are all the same. The first substrates 14 are orthogonal with respect to the second substrates 18 so that the angle A=90.degree. .
FIG. 5 is a somewhat exaggera shows what may happen to the array 28' when the substrates 14 and 18 are not precisely orthogonal that is when the angle A does not equal 90.degree. and when the column spacing S.sub.c is not uniform. Free ends 25 of the unrestrained elements 12 are not uniformly spaced at the planar front end 24 and the array 28' is not symmetrical.
Some attempts have been made to accurately locate and ground the unrestrained elements 12 with the respect to the restrained elements 16. However, such attempts have not been entirely satisfactory because of the great deal of manual work required to align and secure the elements in a periodic array.
In addition to the physical constrains, individual radiator elements 12 and 16 have mechanical and electrical characteristics which require improvement. In particular, the radiators 12 and 16 employ stripline feeds 29 buried within the substrates 14 and 18 which require an impedance match without being too small to economically and reliably manufacture. Bandwidth improvements at the low end, for example 2 GLHz are also desired. Further enhancements in order to reduce VSWR and increase gain are also desired.